With the advent of modern technology, different ways have been developed to perform a pregnancy diagnosis in cattle.
This article will attempt to give an unbiased comparison of the pros and cons of all the different methods currently available. You will find veterinarians all have their own preferred technique, but in specific situations one method may offer distinct advantages over another.
The two most common methods of detecting pregnancy in cattle today are manual rectal palpation, which has stood the test of time, and ultrasound. With the technology improving and the physical size of the machines decreasing, ultrasound has become a lot easier to work with in the large animal field. Other methods such as testing blood or milk samples have a place in limited situations but they cost more and of course involve a time delay in getting the results.
In most situations rectal palpation in beef herds by a skilled veterinarian is fast, efficient, safe and a relatively accurate method during most of the pregnancy. We as veterinarians will tell you it is quite accurate early in the pregnancy (30-100 days) or late (7-9 months). In the middle trimester, while there is no problem telling whether a pregnancy exists, the accuracy as to stage of pregnancy can easily be plus or minus one month or more.
Experienced palpators are fast and gentle so it is a misnomer that damage is caused by touching the fetus especially in late pregnancy. One must be especially gentle in the 30-60 day time frame, especially if the uterus must be flipped back to make the diagnosis. There has been some research that indicates rough palpation at precisely 35 days into a pregnancy leads to a higher incidence of atresia ani (born without a rectum). Further along in pregnancy the fetus is actually quite resilient.
For most beef operations rectal palpation is still the method of choice. As a bonus the veterinarian can also help push cattle up the alleyway vaccinate or apply the endectocide which all help speed up the operation. One needs a palpation cage so the veterinarian is safe and the pregnancy checking can progess quickly. Most veterinarians prefer the cows to be caught. Placing a post behind to keep them from backing up makes for a very dangerous situation if the cow drops down when the vet’s arm is still in the rectum.
Ultrasound is currently used primarily on dairy farms where most pregnancy diagnosis is done early on, in the first 28-70 days. It has a few advantages over rectal palpation at this stage. It is very accurate with these early pregnancies and veterinarians who are experienced with this technique can detect twins and do fetal sexing at 55-70 days of pregnancy. When fetal sexing you need the right view with the ultrasound and this naturally slows down the process.
Very experienced practitioners can diagnose pregnancies in the 27-day range in cattle with ultrasound, and earlier than that in horses You can even detect early embryonic death by noting the lack of a heartbeat in the fetus.
Most often with ultrasound you still go in through the rectum with a probe but less manipulation of the uterus is needed compared to rectal palpation to confirm these early pregnancies. As a result, there is less wear and tear on the arms and wrists of the palpator. The newer machines come with goggles you wear to see the image. This is a great improvement over the older machines that require you to drag a monitor around. When you are working outside the monitor often has to be shrouded from the sunlight so you can see the image on the screen.
Some machines also allow you to take pictures of the images for insurance purposes, which is useful for sales of very high-end animals.
One drawback, of course, is that you are reliant on technology that can break down, so one must always have a backup plan.
In feedlot situations where palpation cages may not be available, inserters can be used which are pushed into the rectum with the probe attached. These are also used to diagnose pregnancy in small ruminants such as alpacas where manual palpation is out of the question.
At auction markets where pregnancies must be staged ultrasound doesn’t have as much value since it is less accurate than palpation with middle and late-stage pregnancies. This is also not the safest area to take expensive equipment that does not stand up well to being bumped or dropped.
Both blood and milk progesterone pregnancy tests have been developed and in certain situations they do have a place. For instance when the veterinarian is unavailable, or veterinary care is distant from the farm a producer could use these tests to detect pregnancy. They are safe because there is no need for the producer to touch the fetus.
The two main drawbacks are cost and the time delay in finding out the results, whereas ultrasound or rectal palpation provide as instant diagnosis so cows can be sorted immediately. Blood and milk tests can also miss early embryonic deaths but generally they are quite accurate unless cattle are tested too early (less than 30 days).
Whatever technique is used, they key point is that pregnancy diagnosis is still a very useful management tool for culling unproductive cows and reducing the winter feed bill in beef herds.
— Dr. Roy Lewis, DVM